γ-aminobutyric acid (GABA), chemical name 4-aminobutyric acid, is also known as aminobutyric acid or piperidinic acid. Its molecular formula is C4H9NO2, and its molecular mass is 103.1. It appears as a white or off-white crystalline powder. It is a hydrophilic amino acid, and its structural formula is as follows:

In mammals, γ-aminobutyric acid is an inhibitory neurotransmitter that mediates more than 40% of inhibitory nerve signals. It has important physiological functions and broad application prospects in pharmaceutical production. In addition, in the food industry, γ-aminobutyric acid can be used in the production of food additives and the development of functional dairy products and bakery products. It can also be employed in sports food and the beverage industry. The Ministry of Health of the People's Republic of China has approved γ-aminobutyric acid as a new resource food.
At present, the research on γ-aminobutyric acid has attracted much attention at home and abroad. Various methods have been employed to prepare different crystalline forms of γ-aminobutyric acid. For example, patents CN101928736A, CN103509831A, CN104531795A have disclosed the preparation of γ-aminobutyric acid via evaporative concentration of a γ-aminobutyric acid fermentation broth, 95% ethanol is then added to the concentrated liquid, followed by stirring, precipitating and crystallization. The product has a crystal morphology that is either needle-shaped or sheet-shaped; it has a dim color and low purity; its main particle size is small, and its particle size is unevenly distributed; it has low bulk density and low flowability, which is not suitable for further processing and use. Patent CN102242161A has disclosed the preparation of γ-aminobutyric acid by a three-effect concentration and direct condensation-crystallization method. The specific steps are: the fermentation broth is evaporated to a certain degree under three different temperature conditions, and then transferred into a vacuum concentration crystallizer, concentrated to obtain the crystals; finally, the crystals are naturally cooled at atmospheric pressure for 1 to 1.5 hours to obtain γ-aminobutyric acid. The crystal morphology of the product is powder-shaped. When exposed to air, the product easily absorbs water and agglomerates into clumps, causing inconveniences in further processing and use. Furthermore, the above preparation procedures are complicated; the preparation method is high in cost and energy consumption, and low in yield, it is not suitable for large-scale industrial production. The chemical reagents used may pose harm to human body and the environment.
Therefore, it is necessary to provide a new crystalline form of γ-aminobutyric acid which is stable, can easily be absorbed and used, does not easily absorb moisture and agglomerate, has large main particle size, uniform particle size distribution, high bulk density and good flowability. It is also necessary to provide a corresponding preparation method which is easy to perform, low in energy consumption, economical, environmentally friendly, and suitable for large-scale industrial production.